The present invention relates to road map databases for use by map-generation and route-finding devices and the like. More particularly, the present invention relates to techniques for combining multiple road map databases into a single combined database.
Map generation and route-finding devices and services are becoming increasingly more common and are gaining widespread use in daily life. Common examples of such devices and services are automobile-based and hand-held navigation systems and Internet-based mapping and route-finding services. It is desirable to have the most complete road data as possible for use with such devices and services. Road map data for use in such systems currently is available from more than one provider. However, no provider is known to provide coverage that is both complete and accurate, for any significantly-sized portion of the United States.
Two well-known providers of road map data are Navigation Technologies (NavTech) of Rosemont, Ill., and Geographic Data Technology, Inc. (GDT) of Lebanon, N.H. The road map data currently available from NavTech is notable for its high accuracy and reliability. The coordinates provided by NavTech are highly consistent with those provided by the Global Positioning System (GPS). The representations of roads in this data set are extremely accurate and very closely reflect the actual roads. However, NavTech""s data set is not complete. Most of the land area of the United States has only partial coverage by NavTech, with data covering only the main highways and extremely sparse coverage of local roads. Currently, various vehicle navigation systems rely upon the NavTech data set. However, the incompleteness of the NavTech data set can create customer dissatisfaction. Customer dissatisfaction can lead to a significant loss of sales of navigation systems, because the data set does not cover areas where customers live and/or travel.
In contrast, the road map data currently available from GDT is much more complete than NavTech""s, with effectively 100% coverage of areas in the United States. However, GDT""s data set has significant geographical position errors as well as geometry problems. Using the GDT data alone in an in-vehicle navigation system, for example, would be a dubious choice, because the GPS system would report very different coordinates for ground positions than the GDT map indicates. GDT data often show extremely inaccurate representations of ramps and complicated road configurations. Because of the discrepancies between the GDT data set and reality, a user of an in-vehicle navigation system using this data could become hopelessly lost quite regularly. GDT data, therefore, has not been used to date for highway navigation.
The present invention includes a machine-implemented method and an apparatus for combining two road map databases. A first road map database and a second road map database have different degrees of coverage and different coverage accuracies for a given geographic region. The two road map databases are accessed, and an output road map database representing a combination of the first road map database and the second road map database is generated.
Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follows.